Apparatus for detecting and marking pin holes



my 1951 G. H. RENDEL 2576,04

APPARATUS FOR DETECTING AND MARKING PIN HOLES Filed lay 19, 1950 'JNQEN E RENDEL Fatented Nov. 20, 1951 APPARATUS FOR DETECTING AND MARKING PIN HOLES George H. Rendel, Pittsburgh, Pa., assignor to United States Steel Company, a corporation of New Jersey Application May 19, 1950, Serial N0. 162,933

This invention relates to apparatus for detecting and marking pin holes in moving strip. Very small holes, known as pin holes, occur in thin strip steel which may be used to make tin plate. These holes are very difiicult to detect. The strip may be inspected for pin holes by means of an electric eye which actuates. a control to mark the defect and also to sort the sheets which are cut from the strip. The speed of the strip varies between 100 and 1000 feet per minute and since there may be a time delay of 0.1 second between the detecting of the hole and the marking thereof, the pin hole is often not marked correctly. In some instances the mark occurs on a sheet adjacent the sheet having the pin hole which causes loss of time in separating the defective sheets.

It is therefore an object of my invention to provide apparatus for detecting and marking pin holes in which means are provided for compensating for variations in strip speed.

This and other objects will be more apparent after referring to the following specification and attached drawing, in which:

The single figure is a schematic view of my apparatus connected in a strip inspecting and shearing line.

Referring more particularly to the drawing the reference numeral 2 indicates an uncoiler for a strip S. The strip S passes from the uncoiler 2 through side trimming knives 4 and measuring rolls 6 to shearing drums 8, where the strip is sheared into sheets S of the desired length. The sheared sheets pass over a conveyor I to a deflector l2 which is operated by means of a solenoid [4 to deflect imperfect sheets to a salvage piler IS. The perfect sheets pass over the deflector l2 to a conveyor l8, which delivers the sheets to a prime sheet piler 20. A high intensity light source 22 is located above the strip adjacent the side trimming knives 4 and a bank of light sensitive photoelectric cells 24 is located in a shielded housing under the light source 22 below the strip. When a section of strip containing a hole passes between the light source 22 and photoelectric cells 24, light passes through the hole and strikes one or more of the photo cells. This generates a small voltage impulse which is transmitted to a voltage amplifier 26 where the impulse is amplified to a value of sufilcient magnitude to operate the controls of the control unit 28. The pin hole detector may be of the type shown in the patent to Chamberlin et al. No. 2,229,638. The control unit 28 converts the short impulse from the amplifier 26 6 Claims. (Cl. 346-33) into an impulse of sufilcient power and duration to operate a solenoid 30 of a strip marker 32 which places a visible mark next to the hole, thus identifying the section of strip containing the hole. The control unit also provides an impulse to energize a solenoid in a proportional timer 34 which is driven by a motor 36 which also drives the measuring rolls 6. Thus the timer 34 is in synchronism with the movement of the strip. The proportional timer 34 is preferably of the type shown in the patent to Ladrach No. 2,217,342 and is equipped with a contact mechanism which energizes the solenoid I4 to tilt the deflector l2 upwardly and direct the sheet containing the pin hole downwardly into the salvage piler IS.

The motor 36 is provided with a shunt field winding 36F which receives current from D. C. power lines 31. The speed of the strip is proportional to the rotational speed of motor 36 and since motor 36 has a constant value of field current through its shunt field winding 36F, the rotational speed of motor 36 is proportional to its armature voltage. Power for driving motor 36 is supplied by a generator 38 which may be driven by any prime mover such as an alternating current induction motor 40. The voltage output from generator 38 is regulated by the strength of its shunt field winding 38F. The current through field winding 38F is controlled by rheostat 42. From the foregoing it will be seen that the strip speed through the processing line is controlled by the rheostat 42 so that the position of contact arm 44 of rheostat 42 may be employed as a reference to indicate strip speed. A motion transmitter 46, such as a Selsyn transmitter, is mechanically connected to contact arm 44 and electrically connected by means of secondary lead wires 48 to a motion receiver 50. Power is supplied to the transmitter 46, receiver 50 and motor 40 from power lines 52. The shaft 54 of receiver 50 has a pinion 56 mounted thereon which is in mesh with the teeth on a rack 58. The rack 58 supports a slidable support 60 on which is mounted the solenoid 30 and marker 32. When contact arm 44 of rheostat 42 is adjusted to change strip speed through the processing line, the motion transmitter 46 will revolve a corresponding amount. This will cause motion receiver 50 to rotate, thus revolving pinion 52 to reposition pinion rack 58 and marker 32 attached thereto. In this manner the marker 32 will be positioned automatically at a distance from the detector to permit marking the strip adjacent the hole regardless of strip speed. The

accumulated inherent delay in the strip marking mechanism may be 0.1 second. Therefore, when the strip speed is 100 feet per minute, the marker 32 should be positioned two inches from the photoelectric cell to permit the marker to function and coincide with passage of the hole.

At 1000 feet per minute the'strip will travel 20 inches in 0.1 second so that the marker 32 must be positioned 20 inches from the photoelectric cell 24 to permit the marker operation to coincide with passage of perforations detected in the strip. The inherent time delay of the strip marking mechanism is constant; therefore, the preferred distance from the detector to the marker is directly proportional to strip speed. The contact arm 44 provides a satisfactory and convenient means to obtain strip speed reference, but other references such as potential sensitive apparatus may be employed to actuate the marker positioning device with equal success.

While one embodiment of my invention has been shown and described, it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claims.

I claim:

1. Apparatus for detecting and marking a pin hole in a moving strip comprising means adjacent the path of travel of said strip for generating a voltage impulse when a pin hole occurs in the strip, a control actuated by said voltage impulse, a strip marker spaced from said means and actuated by said control, means mounting said marker for movement to and away from said first named means, and means for moving said last named means to and away from said first named means as the speed of the strip varies.

2. Apparatus for detecting and marking a pin hole in a moving strip comprising means adjacent the path of travel of said strip for generating a voltage impulse when a pin hole occurs in the strip, a control actuated by said voltage impulse, a strip marker spaced from said means and actuated by said control, means mounting said marker for movement to and away from said first named means, an electric motor rotating at a speed proportional to strip speed, and means responsive to the speed of the motor for moving the marker to and away from said first named means as the speed of the strip varies.

3. Apparatus for detecting and marking a pin hole in a moving strip comprising means adjacent the path of travel of said strip for generating a voltage impulse when a pin hole occurs in the strip, a control actuated by said voltage impulse, a strip marker spaced from said means and actuated by said control, means mounting said marker for movement to and away from said first named means, an electric motor rotating at a speed proportional to strip speed, a generator for supplying current to said motor, a shunt field winding for said generator, means for controlling the current fiow through said shunt field winding, and means responsive to the current flow through said shunt field winding tomove said marker to and away from said first named means as the speed of the strip varies.

4. Apparatus for kletecting and marking a pin hole in a moving strip comprising means adjacent the path of travel of said strip for generating a voltage impulse when a pin hole occurs in the strip, a control actuated by said voltage impulse, a strip marker spaced from said means and actuated by said control, means mounting said marker for movement to and away from said first named means, an electric motor rotating at a speed proportional to strip speed, a generator for supplying current to said motor, a shunt field winding for said generator, a rheostat for controlling the current fiow through said shunt field winding, a contact arm on said rheostat, and means responsive to the position of said contact arm for moving said marker to and away from said first named means as the speed of the strip varies.

5. Apparatus for detecting and marking a pin hole in a moving strip comprising means adjacent the path of travel of said strip for generating a voltage impulse when a pin hole occurs in the strip, a control actuated by said voltage impulse, a strip marker spaced from said means and actuated by said control, means mounting said marker for movement to and away from said first named means, an electric motor rotating at a speed proportional to strip speed, a genera- "tor for supplying current to said motor, a shunt field winding for said generator, means for controlling the current flow through said shunt field winding, a motion transmitting device actuated in accordance to the current flow in said field winding, a, motion receiving device actuated by said motion transmitting device, and means connecting said motion receiving-device to move said marker to and away from said first named means as the speed of the strip varies.

6. Apparatus for detecting and marking a pin hole in a moving strip comprising means adjacent the path of travel of said strip for generating a voltage impulse when a pin hole occurs in the strip, a control actuated by said voltage impulse, a strip marker spaced from said means and actuated by said control, means mounting said marker for movement to and away from said first named means, an electric motor rotating at a speed proportional to strip speed, a generator for supplying current to said motor, a shunt field winding for said generator, a rheostat for controlling the current fiow through said shunt field winding, a contact arm on said rheostat, a motion transmitting device mechanically connected to said arm, a motion receiving device actuated by said motion transmitting device, and means connecting said motion receiving device to move said marker to and away from said first named means as the speed of the strip varies.

GEORGE H. RENDEL.

REFERENCES CITED UNITED STATES PATENTS Name Date Viebahn et a1 June 24, 1941 Number 

